Branched ionomers

ABSTRACT

A branched aromatic ionomer is prepared by co-polymerizing a first monomer having an aromatic moiety and an unsaturated alkyl moiety and a second monomer having an ionic moiety and at least one unsaturated moiety. The ionic moiety may have a cationic group having a valence of +1 or greater. Styrene is among the useful first monomers and sodium methacrylate and zinc dimethacrylate are among the useful second monomers. The branched aromatic ionomers may be used to prepare articles including foamed polystyrene and microwave save dishes and utensils.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to polymers. The present inventionparticularly relates to ionomer polymers.

2. Background of the Art

In the art of preparing polymers, it may be desirable to impart to orincrease the branching of polymer chains. Increased branching may impartphysical property changes to the polymer including increased strength,higher temperature performance, and improved hardness. In someinstances, increased branching may improve properties such aselastomeric performance and abrasion resistance.

Ionomers are known to be useful in many applications. For example, apolyester ionomer dyeability enhancer may be derived from the reactionresidue of an aryl carboxylic acid sulfonate salt, an aromaticdicarboxylic acid, an aliphatic dicarboxylic acid, an aliphatic diol orany of their ester-forming derivatives. A photocurable dental cement maybe prepared using a photocurable ionomer, which is defined as a polymerhaving sufficient pendent ionic groups to undergo a setting reaction inthe presence of a reactive filler and water, and sufficient pendentpolymerizable groups to enable the resulting mixture to be polymerized,e.g., cured upon exposure to radiant energy.

Another ionomer application is in the area of preparing abrasivesurfaces. Ionomers useful in this application are copolymers of ethylenewith unsaturated acid salts such as the zinc salt of acrylic acid.Typical commercial products of this type include Aclyn®, Himiran™,Coathylene®, Surlyn® and Escor® polymers. Surlyn®, of course, is a wellknown component in the covers of some premium golf balls.

SUMMARY OF THE INVENTION

In one aspect, the present invention is a branched aromatic ionomerprepared by co-polymerizing a first monomer having an aromatic moietyand an unsaturated alkyl moiety and a second monomer having an ionicmoiety and at least two unsaturated moieties. In this aspect, the ionicmoiety has at least two ionizable groups, a cationic group that ionizesto form cations and an anionic group that ionizes to form anions and thecationic group is poly-valent and one capable of forming bridges toother molecules in the presence of ions of a suitable type andconcentration.

In another aspect, the present invention is a branched aromatic ionomerprepared by co-polymerizing a first monomer having an aromatic moietyand an unsaturated alkyl moiety and a second monomer having an ionicmoiety and at least one unsaturated moiety. In this aspect, the ionicmoiety has at least two ionizable groups, a cationic group that ionizesto form cations and an anionic group that ionizes to form anions and thecationic group is a mono-valent group.

Another aspect of the present invention is a process for preparing abranched aromatic ionomers. The process includes copolymerizing a firstmonomer having an aromatic moiety and an unsaturated alkyl moiety and asecond monomer having an ionic moiety and at least one unsaturatedmoiety

In still another aspect, the present invention is an article ofmanufacture. The article is formed from a branched aromatic ionomerprepared by co-polymerizing a first monomer having an aromatic moietyand an unsaturated alkyl moiety and a second monomer having an ionicmoiety and at least two unsaturated moieties. In this aspect, the ionicmoiety has at least two ionizable groups, a cationic group that ionizesto form cations and an anionic group that ionizes to form anions and thecationic group is poly-valent and one capable of forming bridges toother molecules in the presence of ions of a suitable type andconcentration.

Another aspect of the present invention is an article of manufacture.The article is formed from a branched aromatic ionomer prepared byco-polymerizing a first monomer having an aromatic moiety and anunsaturated alkyl moiety and a second monomer having an ionic moiety andat least one unsaturated moiety. In this aspect, the ionic moiety has atleast two ionizable groups, a cationic group that ionizes to formcations and an anionic group that ionizes to form anions and thecationic group is a mono-valent group.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed understanding and better appreciation of the presentinvention, reference should be made to the following detaileddescription of the invention and the preferred embodiments, taken inconjunction with the accompanying drawings, wherein:

FIG. 1 is graph of Conversion Versus Time during the runs made inExample 2;

FIG. 2 is a graph of the Molecular Weight Results during the runs madein Example 2;

FIG. 3 is a graph of the Melt Flow Results during the runs made inExample 2;

FIG. 4 is a graph of the Glass Transition Temperature Results during theruns made in Example 2;

FIG. 5 is a graph of the Conversion Verses Time for the runs made inExample 3;

FIG. 6 is a graph of the Molecular Weights Results for the runs made inExample 3;

FIG. 7 is a graph of the Glass Transition Temperature Results for theruns made in Example 3; and

FIG. 8 is a graph of the Melt Flow Results for the runs made in Example3.

It will be appreciated that the figures are not necessarily to scale andthe proportions of certain features may be exaggerated to show detail.

DETAILED DESCRIPTION OF INVENTION

The term “ionomer” is defined in the art of preparing polymers as apolymer with covalent bonds between elements of the polymer chain andionic bonds between the separate chains of the polymer. Ionomer is alsodefined as polymers containing inter-chain ionic bonding. Thermoplasticionomers have the unique property of forming reversible crosslinks. Atmelt processing temperatures, crosslinks disassociate to later reform asthe material cools to its glass transition temperature.

Branched aromatic ionomers may be formed by co-polymerizing a firstmonomer having an aromatic moiety and an unsaturated alkyl moiety and asecond monomer having an ionic moiety and at least one unsaturatedmoiety. For example, suitable first monomers having an aromatic moietyand an unsaturated alkyl moiety may include monovinylaromatic compoundssuch as styrene as well as alkylated styrenes wherein the alkylatedstyrenes are alkylated in the nucleus or side-chain. Alphamethylstyrene, t-butylstyene, p-methylstyrene, methacrylic acid, and vinyltoluene are suitable first monomers that may be useful for preparingbranched aromatic ionomers. The monovinylaromatic compounds may beemployed singly or as mixtures. In one embodiment, styrene is usedexclusively as the first monomer. Any monomer having an aromatic moietyand an unsaturated alkyl moiety may be used to prepare the branchedaromatic ionomers.

The second monomer has an ionic moiety and at least one unsaturatedmoiety. The ionic moiety has at least two ionizable groups, one groupthat ionizes to form cations and one that ionizes to form anions. In oneembodiment, the group that ionizes to form cations, hereinafter“cationic group,” is a mono-valent group. In another embodiment, thecationic group is poly-valent and one capable of forming bridges toother molecules in the presence of ions of a suitable type andconcentration.

When the cationic group in the second monomer is a mono-valent group, itis a mono-valent metal or a quaternary ammonium ion forming compound.Suitable metals include sodium, potassium, cesium, silver, and the like.Suitable quaternary ammonium compounds include ammonium chloride, methylammonium chloride, diethyl ammonium chloride, and the like.

When the cationic group is one capable of forming bridges to othermolecules in the presence of ions of a suitable type and concentration,it is a group that ionizes to form cations having a valence of +2 orhigher. In one embodiment, the cationic group may be a metal having anoxidation state of +2 or higher. Suitable metals include zinc, copper,lead, calcium, magnesium, zirconium, aluminum, and the like.

The second ionizable group is an organic group that ionizes to form ananion having a coordination charge of −1 or lower. Suitable groupsinclude the anions of amines, carboxylic acids, sulfonic acids,phosphonic acids, thioglycolic acids and the like. When the cationicgroup has a valence of greater than +1, the first and second ionizablegroups may form a bridge.

The anionic group includes at least one polymerizable unsaturatedmoiety. In some embodiments, there is only one. In other embodiments,there may be two or more such moieties. The unsaturated moiety may be aterminal or non-terminal carbon—carbon double bond.

Exemplary compounds useful as the second monomer may be prepared with ametal cation and an organic anion having at least one unsaturation.Suitable compounds that may be used as the second monomer include anyhaving a general formula:

wherein R is a hydrocarbon chain having from 2 to 40 carbons and atleast one polymerizable unsaturation; A is an anionic group; M is acationic group; Z is −1 or −2; X is +1, +2, +3, +4, or +5; and y is aninteger having a value of from 1 to 4.

When y is 1, R may have one or more polymerizable unsaturations. Inembodiments where y is 1, R may have two or more unsaturations and theunsaturations will either be on separate chains or else sufficiently farapart on a single chain to allow for polymerization without substantialsteric hindrance. In some embodiments, (y*Z)+X=0, that is, only anionicgroups having a polymerizable unsaturation will be coordinated to the Mgroup, however it is within the scope of the claims that additionalgroups not having a polymerizable unsaturation may be coordinated to theM group. When this occurs, there may still be at least two polymerizableunsaturations coordinated to the M group in addition to any othercoordinated groups.

Compounds that may be used as the second monomer of the presentinvention include, but are not limited to: zinc alkoxide, zinc butoxide,zinc diacrylate, zinc dimethacrylate, zinc di-vinylacetate, zincdi-ethylfumarate, and the like; calcium carbonate; copper diacrylate,copper dimethacrylate, copper di-vinylacetate, copper di-ethylfumarate,and the like; aluminum triacrylate, aluminum trimethacrylate, aluminumtri-vinylacetate, aluminum tri-ethylfumnarate, aluminum(III)isopropoxide, and the like; zirconium tetraacrylate, zirconiumtetramethacrylate, zirconium tetra-vinylacetate, zirconiumtetra-ethylfumarate, zirconium(IV) butoxide and the like. For compoundshaving monovalent cationic groups, the second monomer may be sodiumacrylate, sodium methacrylate, sodium ethoxide, silver methacrylate, andthe like. These compounds and any compound useful as the second monomermay be prepared by, for example, reacting an organic acid or ananhydride with a metal or metal salt. When the cation group ispolyvalent, then the organic acid and the polyvalent metal may bereacted under conditions sufficient to prepare a bridge between theanionic group and the cationic group. Compounds useful as the secondmonomer may be prepared by any method known to those of ordinary skillin the art of preparing monomers to be useful.

The monomers used to prepare the branched aromatic ionomers may interactin several ways to affect the physical properties of the ionomers. Afirst way is the formation of covalent bonds due to the polymerizationof the unsaturated moieties.

A second way that the monomers used to prepare the branched aromaticionomers may interact is by the formation of a bridge wherein apolyvalent cationic group is coordinated to two anionic groups which areintegrated into the backbones of at least two separate chains. Thiscoordination may, in effect, cross link the two chains therebyincreasing that segment's total effective molecular weight to the sum ofthe two chains.

A third way that that the monomers used to prepare the branched aromaticionomers may interact is by the formation of multiple bridges asdescribed immediately above. The more crosslinking that occurs, the lessflexible the three dimensional structure of the ionomer, which mayresult in lower melt flow values and increased melt strength.

In yet a fourth way of interacting, when the cationic groups aremono-valent, the ionic moieties, while not fully bridged, may stillassociate due to hydrophobic-hydrophilic forces. In these embodiments,this weaker but still measurable force may result from the comparativelynon-polar hydrophobic, non-ionic parts of the molecule being mutuallyattracted and repelled from the polar hydrophilic ionic parts of theionomer. These forces are more noticeable as the proportion of thesecond monomer is increased in concentration. These four are not all ofthe possible interactions of the monomers. In addition, most of theproperties of the ionomers associated with its primary, secondary, andeven tertiary structure, such as the ionomers' glass transitiontemperatures “Tg” may be affected.

Both the amount of second monomer and the type of interaction with thefirst monomer will dictate the amount of second monomer used. Therefore,in some embodiments where the interaction is weak, such as when thecationic group of the second monomer is mono-valent, and a significantamount of effect is desired from the second monomer, the branchedionomers are prepared with a comparatively large amount of the firstmonomer, typically with a ratio of first monomer to second monomer offrom about 999:1 to about 40:60. In other such embodiments, the ratio isfrom about 95:5 to about 50:50. In still other such embodiments, theratio is from about 90:10 to about 60:40. Other embodiments have a ratioof from 80:20 to 70:30. Where the interaction is very strong, such aswhen the cationic group is di- or tri-valent, or only small changes tothe properties of the ionomer due to the second monomer are desired, theamount of the second monomer is quite small ranging from about 10 partsper million “ppm” to about 10,000 ppm. In other such ionomers, the rangeis from about 100 ppm to about 1000 ppm. In still other such ionomers,the range is from about 250 ppm to about 800 ppm.

The branched aromatic ionomer is prepared by co-polymerizing the firstand second monomers. Each of these monomers has at least onepolymerizable unsaturation. The polymerization may be carried out usingany method known to those of ordinary skill in the art of performingsuch polymerizations. For example, the polymerization may be carried outby using a polymerization initiator.

Examples of the polymerization initiators are, for instance, radicalpolymerization initiators such as benzoyl peroxide, lauroyl peroxide, t-butyl peroxybenzoate and 1,1-di-t-butylperoxy-2,4-di-t-butylcyclohexane.The amount of the polymerization initiator is from about 0 to about 1percent by weight of the monomers. In one embodiment, the amount ofpolymerization initiator is from about 0.01 to about 0.5 percent byweight of the monomers. In another embodiment, the amount ofpolymerization initiator is from about 0.025 to about 0.05 percent byweight of the monomers.

Alternatively, rather than using an initiator, the ionomer may beprepared using heat as an initiator. The ionomer may be prepared using anon-conventional initiator such as a metallocene catalyst as isdisclosed in U.S. Pat. No. 6,706,827 to Lyu, et al., which isincorporated herein in its entirety by reference. In one embodiment, themonomers may be admixed with a solvent and then polymerized. In anotherembodiment, one of the monomers is dissolved in the other and thenpolymerized. In still another embodiment, the monomers may be fedconcurrently and separately to a reactor, either neat or dissolved in asolvent, such as mineral oil. In yet another embodiment, the secondmonomer may be prepared in-situ or immediately prior to thepolymerization by admixing the raw material components, such as anunsaturated acid or anhydride and a metal alkoxide, in-line or in thereactor. Any process for polymerizing monomers having polymerizableunsaturation know to be useful to those of ordinary skill in the art inpreparing such polymers may be used. For example, the process disclosedin U.S. Pat. No. 5,540,813 to Sosa, et al., may be used and isincorporated herein in its entirety by reference. The processesdisclosed in U.S. Pat. No. 3,660,535 to Finch, et al., and U.S. Pat. No.3,658,946 to Bronstert, et al., may be used and are both incorporatedherein in their entirety. Any process for preparing general purposepolystyrene may be used to prepare the branched aromatic ionomerionomers.

In certain embodiments, the ionomers may be admixed with additives priorto being used in end use applications. For example, the ionomers may beadmixed with fire retardants, antioxidants, lubricants, blowing agents,UV stabilizers, antistatic agents, and the like. Any additive known tobe useful to those of ordinary skill in the art of preparing ionomers tobe useful may be used with the branched ionomers.

The ionomers are useful as general purpose polystyrene, but may also beused in other applications. They may be foamed to prepare foamedpolystyrene. The ionomers may be used in applications where hightemperature performance is desirable such as microwave safe dishes andutensils. The ionomers may be used to form other objects such ascontainers and as components in automobiles, toys, and the like. Thepolar ionic moieties of the ionomers may enhance their compatibilitywith polyesters such as polyethylene terephthalate and polycarbonate, sothe branched ionomers may be used in blends and alloys with these andother similarly polar polymers.

EXAMPLES

The following examples are provided to illustrate the present invention.The examples are not intended to limit the scope of the presentinvention and they should not be so interpreted. Amounts are in weightparts or weight percentages unless otherwise indicated.

Example 1

Polystyrene homopolymer is prepared using a stirred 500 ml reactionkettle. The polymerization is initiated using a LUPERSOL® 233 catalystat a concentration of about 170 ppm. The reaction is run at about 267°F. (131° C.). The initial melt flow of the polystyrene is 3.7 dg/minute.The second monomer Zinc dimethacrylate “ZnMA” is added in stages byfirst dissolving the ZuMA in styrene, the first monomer, and thenfeeding the solution to the reactor. The reactor was allowed tostabilize and samples 1-A. 1-B, and 1-C were collected at points wherethe concentration of ZnMA in styrene is 400 ppm, 600 ppm and 800 ppm.The samples are tested and the results shown below in Table 1.

Example 2

Example 1 is repeated substantially identically except that the reactionis run at 275° F. (135° C.), and 175 ppm of LUPERSOL® 233 catalyst, andthe components shown in Table 2 are used. The n-dodecyl mercaptan (NDM),serves as a chain transfer agent. Samples 2-A, 2-B, 2-C, 2-D, and 2Ewere tested and the results shown below in Table 2.

Example 3

Four samples of Polystyrene were prepared using a constant concentrationof methacrylic acid using the same procedure and apparatus as in Example2 except that the acid is neutralized in the feed with one of the secondmonomers that have different valences: sodium ethoxide, calciumcarbonate, aluminum(III) isopropoxide, and zirconium(IV) butoxide, andthe LUPERSOL® 233 catalyst is used at a concentration of 200 ppm.Samples 3-A, 3-B, 3-C, and 3-D were tested and the results shown belowin Table 3.

TABLE 1 Example 1-A Example 1-B Example 1-C [ZnMA] ppm 400 600 800 MFI¹NA 3.84 3.51 Flex Strength² NA 13,808/95.2  13,377/92.2  TensileStrength Yld³ NA 7,421/51.2  7,409/51.1 Tensile Strength Brk³ NA7326/50.5  7,290/50.5 Elongation³ NA 3.0 2.5 Vicat⁴ NA 220/104  220/104Mn⁵ 94 95 94 Mw⁵ 249 298 315 Mz⁵ 424 1978 2,433 Polydispersity⁶ 2.6 3.23.3 ¹ASTM D-1238 g/10 min, 200 C/5 kg, October 2001. ²ASTM D-790psi/MPa, January 2001 ³ASTM D-638 psi/MPa, psi, %, September 2001 ⁴ASTMD-1525, F/C, May 2000 ⁵ASTM D-6474 ⁶Mz/Mn

TABLE 2 Comp-2* 2-A 2-B 2-C 2-D 2-E [ZnMA] 0 1200 1200 1800 4000 5000ppm NDM ppm 0 0 100 150 440 550 MFI¹ 4.4 3.2 4.0 2.8 0.8 0.7 Tg² 107 114113 113 109 113 Mn³ 107 108 93 96 97 93 Mw³ 222 269 307 354 413 405 Mz³335 1867 3754 4963 4763 4849 Poly- 2.1 2.5 3.3 3.7 4.2 4.3 dispersity⁴¹ASTM D-1238 g/10 min, 200 C/5 kg, October 2001. ²ASTM D-3418, C, DSCInflection (Mid) Point, July 1999. ³ASTM D-6474 ⁴Mz/Mn. *Not an exampleof the invention.

TABLE 3 3-A 3-B 3-C 3-D Comp-3* Na Salt Ca Salt Al Salt Zr SaltMethacrylic Acid, ppm NA 1269 1269 1269 1269 Sodium, ppm¹ NA 339 NA NANA Calcium, ppm² NA NA 295 NA NA Aluminum, ppm³ NA NA NA 132 NAZirconium, ppm⁴ NA NA NA NA 336 Melt Flow⁵ 2.90 2.89 2.70 1.80 0.51 Tg⁶107.5 108.0 108.6 109.3 109.7 Mn⁷ 124,563 119,328 126,800 129,454114,417 Mw⁷ 256,581 262,625 285,875 608,260 1,044,123 Mz⁷ 391,336400,917 613,472 6,737,117 10,494,556 PDI⁸ 2.1 2.2 2.3 4.7 9.1 ¹as sodiumethoxide ²as calcium carbonate ³aluminum(III)isopropoxide⁴zirconium(IV)butoxide ⁵ASTM D-1238 g/10 min, 200 C/5 kg, October 2001.⁶ASTM D-3418, C, DSC Inflection (Mid) Point, July 1999. ⁷ASTM D-6474⁸Mz/Mn. *Not an example of the invention.Discussion of the Figures

FIGS. 1–4 are graphical representations of the values recorded relatingto Example 2. Therein, zinc di-methacrylate is shown to be an effectivedi-functional monomer to induce chain-branching and to increase thez-average molecular weight in polystyrene. Levels as low as 200 ppmincreased the z-average molecular weight of the polystyrene to close to1,000,000 g/mol. Despite the efficiency of this monomer as acrosslinking agent, the resulting polymers did not show signs ofgelation at levels of addition producing molecular weights of up to6,000,000 g/mol.

FIGS. 4–8 are graphical representations of the values recorded relatingto Example 3. They show that various salts of methacrylic acid may besynthesized, in-situ, in the polymer feed, prior to polymerization. Theyalso show that in going from a mono-valent to a tri-, or tetra-valentcounter-ion, the weight average molecular weight is observed to doubleor triple, the and z-average molecular weight is observed to increase upto 20 fold. It is observed that in going to higher valence states, theincrease in molecular weight is accompanied by a decrease in the meltflow, however, even for molecular weights of 1,000,000 g/mol, thematerial still flows.

1. A branched aromatic ionomer comprising the product of co-polymerizinga first monomer comprising an aromatic moiety and an unsaturated alkylmoiety and 1 pph or less of a second monomer comprising an ionic moietyand at least two unsaturated moieties, wherein the ionic moiety has atleast two ionizable groups, a cationic group that ionizes to formcations and an anionic group that ionizes to form anions, and whereinthe cationic group is poly-valent and one capable of forming bridges toother molecules; and wherein the second monomer is comprised of acompound having a formula of:

 where: R is a hydrocarbon chain having from 2 to 7 carbons and at leastone polymerizable unsaturation, A is an anionic group, M is a cationicgroup, Z is −1 or −2, X is +1, +2, +3, +4, or +5, and y is an integerhaving a value of from 1 to
 4. 2. The branched aromatic ionomer of claim1 wherein the first monomer is selected from the group consisting ofalphamethyl styrene, t-butylstyrene, p-methylstyrene, vinyl toluene, andmixtures thereof.
 3. The branched aromatic ionomer of claim 1 whereinthe second monomer is selected from the group consisting of: zincdiacrylate, zinc dimethacrylate, zinc di-vinylacetate, zincdi-ethylfumarate: copper diacrylate, copper dimethacrylate, copperdi-vinylacetate, copper di-ethylfumarate; aluminum (III) isopropoxide,aluminum triacrylate, aluminum trimethacrylate, aluminumtri-vinylacetate, aluminum tri-ethylfumarate; zirconium tetraacrylate,zirconium tetramethacrylate, zirconium tetra-vinylacetate, zirconiumtetra-ethylfumarate, zirconium (IV) butoxide; and mixtures thereof. 4.The branched aromatic ionomer of claim 1 wherein the second monomer iszirconium (IV) butoxide or zinc diacrylate.
 5. The branched aromaticionomer of claim 1 wherein the second monomer is zinc dimethacrylate orzinc diacrylate.
 6. A branched aromatic ionomer comprising the productof co-polymerizing a first monomer comprising an aromatic moiety and anunsaturated alkyl moiety and 1 pph or less of a second monomercomprising an ionic moiety and at feast one unsaturated moiety, whereinthe ionic moiety has at least two ionizable groups, a cationic groupthat ionizes to form cations and an anionic group that ionizes to formanions, and wherein the cationic group is a mono-valent group; andwherein the second monomer is comprised of a compound having a formulaof:

 where: R is a hydrocarbon chain having from 2 to 7 carbons and at leastone polymerizable unsaturation, A is an anionic group, M is a cationicgroup, Z is −1 or −2, X is +1, +2, +3, +4, or +5, and y is an integerhaving a value of from 1 to
 4. 7. The branched aromatic ionomer of claim6 wherein the first monomer is selected from the group consisting ofalphamethyl styrene, t-butylstyene, p-methylstyrene, vinyl toluene, andmixtures thereof.
 8. The branched aromatic ionomer of claim 6 whereinthe second monomer is selected from the group consisting of sodiumacrylate, sodium methacrylate, sodium ethoxide, silver methacrylate, anda combination thereof.
 9. The branched aromatic ionomer of claim 1 wherethe cationic group is selected from the group consisting essentially of:zinc, copper, lead, calcium, magnesium, zirconium, aluminum, and acombination thereof.
 10. An article made from the branched aromaticionomer of claim
 1. 11. The branched aromatic ionomer of claim 1 whereinsaid ionomer is foamed, and wherein said foamed ionomer is used to makean article.
 12. The branched aromatic ionomer of claim 6 where thecationic group is selected from the group consisting of: sodium,potassium, cesium, silver, and a combination thereof.
 13. The branchedaromatic ionomer of claim 6 where the cationic group is a quaternaryammonium forming compound.
 14. An article made from the branched ionomerof claim
 6. 15. The branched aromatic ionomer of claim 7 wherein saidionomer is foamed, and wherein said foamed ionomer is used to make anarticle.
 16. A branched aromatic ionomer comprising the product ofco-polymerizing a first non-ionic monomer comprising styrene and 1 pphor less of a second monomer comprising an ionic moiety and at least twounsaturated moieties, wherein the ionic moiety has at least twoionizable groups, a cationic group that ionizes to form cations and ananionic group that ionizes to form anions, and wherein the cationicgroup is poly-valent and one capable of forming bridges to othermolecules; and wherein the second monomer is comprised of a compoundhaving a formula of:

 where: R is a hydrocarbon chain having from 2 to 7 carbons and at leastone polymerizable unsaturation, A is an anionic group, M is a cationicgroup, Z is −1 or −2, X is +1, +2, +3, +4, or +5, and y is an integerhaving a value of from 1 to
 4. 17. The branched aromatic ionomer ofclaim 16 wherein the second monomer is selected from the groupconsisting of: zinc diacrylate, zinc dimethacrylate, zincdi-vinylacetate, zinc di-ethylfumarate; copper diacrylate, copperdimethacrylate, copper di-vinylacetate, copper di-ethylfumarate;aluminum (III) isopropoxide, aluminum triacrylate, aluminumtrimethacrylate, aluminum tri-vinylacetate, aluminum tri-ethylfumarate;zirconium tetraacrylate, zirconium tetramethacrylate, zirconiumtetra-vinylacetate, zirconium tetra-ethylfumarate, zirconium (IV)butoxide; and mixtures thereof.
 18. The branched aromatic ionomer ofclaim 16 wherein the second monomer is selected from the groupconsisting of: zinc diacrylate, zinc dimethacrylate, zincdi-vinylacetate, zinc di-ethylfumarate, zinc alkoxide, and combinationsthereof; and where the average molecular weight (Mn) of said ionomer is114,000 or less.
 19. An article made from the branched aromatic ionomerof claim
 16. 20. The branched aromatic ionomer of claim 16 wherein saidionomer is foamed, and wherein said foamed ionomer is used to make anarticle.
 21. A branched aromatic ionomer of claim 6, where theunsaturated moiety is a terminal or non-terminal carbon—carbon doublebond.
 22. A branched aromatic ionomer of claim 1, further comprised of apolymerization initiator.
 23. A branched aromatic ionomer of claim 6,further comprised of a polymerization initiator.
 24. A branched aromaticionomer of claim 16, further comprised of a polymerization initiator.25. A branched aromatic ionomer of claim 16, further comprised of achain transfer agent.
 26. A branched aromatic ionomer of claim 16,further comprised of a polymerization initiator and a chain transferagent.